A consumer unit is a box of fuses or breakers, usually arranged in a single row. This is unlike a distribution board which has multiple rows of fuses or breakers and usually serves two or more locations, which may be split phase, two phase, two phases taken from three phase, or three phases.
A consumer unit fitted with just fuses is often referred to as a "fuse box".
"Consumer Unit (may also be known as a consumer control unit). A particular type of distribution board comprising a type-tested co-ordinated assembly for the control and distribution of electrical energy, principally in domestic premises, incorporating manual means of double-pole isolation on the incoming circuit(s) and an assembly of one or more fuses, circuit breakers, residual current operated devices or signalling and other devices proven during the type-test of the assembly as suitable for use." 
Modern consumer units (picture bottom right) usually use DIN-rail mount breakers. The rail and the shape of the front opening are standardized but the busbar arrangements are not. Therefore mixing of brands should generally be avoided and, where unavoidable, care should be taken to ensure that the breaker chosen is a good fit for the busbars.
Generally a "split load" arrangement is used with some circuits protected by the RCD and others not.
The box pictured top-right is a "Wylex standard" fitted with rewirable fuses. These boxes can also be fitted with cartridge fuses or miniature circuit breakers (MCBs). This type of consumer unit was very popular in Britain until 2001 when wiring regulations mandated residual current device (RCD) protection for sockets that could "reasonably be expected to" supply outdoor equipment (BS7671:2001, ISBN 0-86341-373-0). There were a number of similar designs from other manufacturers but the Wylex ones are by far the most commonly encountered and the only ones for which fuseholders/breakers are still commonly available.
RCD protection types
With the introduction of the recent 17th Edition IEE Wiring Regulations consumer units in the UK must provide RCD protection to all cables embedded in walls excepting high integrity circuits such as those for burglar alarms or smoke alarms.
Consumer units have different methods of protecting circuits. A dual split-load consumer unit can be arranged as follows:
- Upstairs Lights,
- Downstairs Final Ring Main,
- Garage Sockets,
- Downstairs Lights,
- Upstairs Sockets,
By alternating the circuits like this, power will always be present on one floor if either RCD trips out.
Another way to protect circuits under the 17th Edition IEE Wiring Regulations is by fitting Residual Current Circuit Breaker With Overload (RCBOs) to every circuit although this can be a very costly method.
Some older systems such as those that use MK or old MEM Consumer Units that used fuses had one fuse per spur so for instance:
- Upstairs Lights Fuse 1
- Upstairs Sockets Fuse 2
- Downstairs Lights Fuse 3
- Downstairs Sockets Fuse 4
- ^ IEE Wiring Regulations Seventeenth Edition - British Standard BS7671:2008, Part 2 Definitions
Wikimedia Foundation. 2010.
Look at other dictionaries:
Consumer unit (economics) — In economics, a consumer unit is defined as either (1) all members of a particular household who are related by blood, marriage, adoption, or other legal arrangements; (2) a person living alone or sharing a household with others or living as a… … Wikipedia
Consumer Expenditure Survey — The Consumer Expenditure Survey (CE) is a Bureau of Labor Statistics (BLS) survey that collects information on the buying habits of U.S. consumers. The program consists of two components the Interview Survey and the Diary Survey each with its own … Wikipedia
Consumer Product Safety Improvement Act — Consumer Safety Act Full title Consumer Product Safety Improvement Act Acronym CPSIA Colloquial name(s) Consumer Act Enacted by the 110th United States Congress Effective … Wikipedia
Consumer IR — Consumer IR, consumer infrared, or CIR, refers to a wide variety of devices employing the infrared electromagnetic spectrum for wireless communications. Most commonly found in television remote controls, infrared ports are equally ubiquitous in… … Wikipedia
Consumer Affairs Victoria — (CAV) is a Victorian government agency that protects and promotes the interests of consumers and is based in the Australian state of Victoria. CAV is responsible for reviewing and advising the Victorian Government on consumer legislation and… … Wikipedia
Consumer confidence — is an economic indicator which measures the degree of optimism that consumers feel about the overall state of the economy and their personal financial situation. How confident people feel about stability of their incomes determines their spending … Wikipedia
Consumer theory — is a theory of microeconomics that relates preferences to consumer demand curves. The link between personal preferences, consumption, and the demand curve is one of the most complex relations in economics. Implicitly, economists assume that… … Wikipedia
Consumer economics — is a branch of economics. It is a broad field, principally concerned with microeconomic analysis behavior in units of consumers, families, or individuals (in contrast to traditional economics, which primarily government or business units). It… … Wikipedia
Consumer Protection Act. (CPA) South Africa — The Consumer Protection Act, No. 68 of 2008 was signed on 24 April 2009. It aims to: • Promote a fair, accessible and sustainable marketplace for consumer products and services; • Establish national norms and standards to ensure consumer… … Wikipedia
Consumer choice — Economics … Wikipedia